Removing automaticly generated (automatic weights) weight paint
What causes the problem is the Mirror modifier in the shoes. The Vertex Groups option of Mirror modifier is on by default, and it's unchanged here. That option mirrors weight in vertex groups with symmetrical names. That is, for every pair of vertex groups suffixed with .L and .R, Blender will just match vertex weights in both, even if you only assign weights to one of them.

The problem is, Blender assumes the object's symmetry coincides with armature name symmetry, while your objects are not. Instead of mirroring the left shoe for the right shoe, thereby matches the armature's shoe.L and shoe.R and works as expected, you're mirroring each half of each shoe.

The solution is easy: For each foot, either delete the (unused) vertex group for the other foot, uncheck Vertex Groups in the Mirror modifier's setting, or apply the Mirror modifier.